This commit and, by extension, PR attempts to update `stb` in the most
straightforward way possible as well as include fixes from main repo's
unmerged PRs for cases rearing their ugly heads during everyday usage:
- stb#1299: stb_rect_pack: Make rect_height_compare a stable sort
- stb#1402: stb_image: Fix "unused invalid_chunk" with STBI_FAILURE_USERMSG
- stb#1404: stb_image: Fix gif two_back memory address
- stb#1420: stb_image: Improve error reporting if file operations fail
within *_from_file functions
- stb#1445: stb_vorbis: Few static analyzers fixes
- stb#1487: stb_vorbis: Fix residue classdata bounding for
f->temp_memory_required
- stb#1490: stb_vorbis: Fix broken clamp in codebook_decode_deinterleave_repeat
- stb#1496: stb_image: Fix pnm only build
- stb#1497: stb_image: Fix memory leaks if stbi__convert failed
- stb#1498: stb_vorbis: Fix memory leaks in stb_vorbis
- stb#1499: stb_vorbis: Minor change to prevent the undefined behavior -
left shift of a negative value
- stb#1500: stb_vorbis: Fix signed integer overflow
Includes additional small fixes that I felt didn't warrant a separate PR.
